While online banking and money management tools can help you get a handle on tracking expenses, keeping track of cash expenses can be more difficult. But if you set up a Twitter account (and I'd recommend making it a private one) you can use Tweet What You Spend to send notes on what and how much you've spent on purchases from your mobile phone. The updates are cataloged on a spending journal, and you can download the information as a spreadsheet so that you can import it into another personal finance application. After the jump, an introductory video from the creators offers a step-by-step video to getting the service set up.